The present application relates to an optical oscillation device emitting laser light and a recording apparatus using the optical oscillation device.
In recent years, larger capacity and higher speed of communication have been necessary with the development of IT in society. Therefore, with regard to media used to propagate information, optical communication technologies using not only radio waves with frequencies of, for example, a 2.4 GHz band and a 5 GHz band, as in radio communication, but also light with a wavelength of, for example, a 1.5 μm band (up to hundreds of THz in frequency) have rapidly come into wide use.
For example, a method of transmitting information by light is used not only for optical communication such as optical fiber communication but also for recording and reproducing information on and from recording media. Therefore, optical information technologies will become an important basis for supporting the development of the future information society.
When information is transmitted or recorded by light, a light source that oscillates specific pulses is necessary. In particular, high-output and short-pulsed light sources are indispensable in communication and for large capacity and high speed of recorded and reproduced information, and thus various semiconductor lasers have been studied and developed as the light sources that satisfy the large capacity and high speed of the information.
For example, when reproduction from an optical disc is performed using a single-mode laser, noise may occur due to interference of an optical system and an oscillation wavelength may also be changed due to a change in temperature, and therefore output variation or noise may occur.
Accordingly, a high-frequency superimposing circuit performs a modulation process of changing the mode of a laser to a multi-mode from the outside to suppress an output variation caused due to a change in temperature or due to light returned from an optical disc. However, this method may lead to an increase in the size of an apparatus in proportion to addition of the high-frequency superimposing circuit, and thus may lead to an increase in cost.
In a self-excited oscillation semiconductor laser, however, the output variation can be suppressed even without using the high-frequency superimposing circuit, since multi-mode oscillation can be directly realized by blinking a light source at a high frequency.
For example, a light source capable of achieving an oscillation output of 10 W and a pulse width of 15 psec at a frequency of 1 GHz has been realized using a self-excited oscillation GaN violet-blue semiconductor laser (for example, see Applied Physics Express 3, (2010) 052701 by Hideki Watanabe, Takao Miyajima, Masaru Kuramoto, Masao Ikeda, and Hiroyuki Yokoyama).
This semiconlductor laser is a tri-sectional self-excited oscillation semiconductor aser that includes a saturable absorber section and two gain sections between which the saturable absorber section is interposed.
This semiconductor laser applies a reverse bias voltage to the saturable absorber section. At this time, laser light with a wavelength of, for example, 407 nm is emitted by injecting a current into the two gain sections.